Refrigeration method and apparatus embodying fluid expansion



June 15, 1965 w, H, HOGAN 3,188,818

REFRIGERATION METHOD AND APPARATUS EMBODYING FLUID EXPANSION Filed NOV. 12, 1963 2 Sheets-Sheet 1 Fig. 2

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Y INVENTOR. 5 Walter H. Hogan Attorney June 15, 1965 w. H. HOGAN 3,183,813

REFRIGERATION METHOD AND APPARATUS EMBODYING FLUID EXPANSION Filed Nov. 12, 1963 2 Sheets-Sheet 2 l2 UP 30 DISPLACER DOWN S'OPEN VALVE 6| (FIG. 9)

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INVENTOR.

Attorney United States Patent Ofifice 3,188,818 Patented June 15, 1965 REFRIGERATION METHOD AND APPARATUS L EMBODYIN G FLUID EXPANSION Walter H. Hogan, Wayland, Mass, assignor to Arthur D.

Little, Inc., Cambridge, Mass, a corporation of Massachusetts Filed Nov. 12, 1963, Ser. No. 322,731 16 Claims. (Cl. 62-6) This invention relates to method and apparatus for developing low-temperature refrigeration and more particularly to refrigeration method and apparatus which incorporate fluid expansion and operate on the so-called no-work type of cycle.

In United States Patent No. 2,966,035 issued to Gifford, .there is described refrigeration method and apparatus directed to a so-called no-work cycle in which refrigeration is obtained by removing more sensible heat from a system than is taken into the system by the refrigerating fluid used. Although the cycle described in U.S.P. 2,966,035 has been found to be very successful in producing refrigeration even as low as K., the cycle possesses inherent disadvantages. First, it is necessary to operate with a .sizcable temperature difference across the regenerator.

Second, there exists a pressure drop through the regenerator, as well as a pressure drop across the displacer. The pressure drop across the regenerator, and hence across the displacer, is subject to increase by reason of contamination build-up within the regenerat-or. Finally such pressure drops inflict an undue burden on the drive mech anism of the refrigeration apparatus inasmuch as they intensify the tendency of the displacer to move in a direction opposite to that in which it must be driven to operate the refrigerator.

it would therefore be desirable to have a no-work cycle and apparatus which make possible the minimizing of the pressure drop within the regenerator and across the displacer and the temperature differential across the regenerator. This in turn would decrease the burden on the mechanical driving system, and would result in the achievement of greater efficiencies in refrigeration than is obtained in the present no-work cycle.

It is therefore the primary object of this invention to provide an improved no-work cycle and apparatus. It is another object of this invention to provide a cycle and apparatus of the character described in which the temperature diflerential and the pressure drop across the regenerator is minimized and the mechanical shocks to the system are minimized. It is another object to provide 'such apparatus and method in which the pressure drop across the displacer is decreased. It is another object to provide apparatus and method of the character described capable of being incorporated in miniaturized equipment and achieving refrigeration down to about 10 K. It is still another object of this invention to provide apparatus which is also adaptable to large-scale equipment in which mechanical shocks are minimized and mechanical wear is reduced below that now experienced by the present nowork apparatus. Other objects of the invention will in part be obvious and will in part be apparent hereinafter.

The invention accordingly comprises the several steps and the relation of one or more of such steps with respect to each of the others, and the apparatus embodying features of construction, combinations of elements, and arrangement of parts which are adapted to eflect such steps, all as exemplified in the following detailed disclosure, and the scope of the invention will be indicated in the claims.

For a fuller understanding of the objects of the invention, reference should be had to the following detailed description taken in connection with the accompanying "drawin gs in which FIGS. 1-4 are simplified diagrammatic views of the apparatus of this invention illustrating the steps in the basic cycle;

FIG. 5 is a simplified drawing of a refrigeration apparatus in which the energy delivered external of the sys tem is part thermal and part mechanic-a1;

FIGS. 6-8 illustrate modifications in the types of regenerators which may be used in the apparatus;

FIG. 9 is a modification of the apparatus of FIG. 1 incorporating an auxiliary fluid conduit and valve;

FIG. 10 is an operational sequence diagram of the ap paratus of FIG. 9 showing the opening and closing of the auxiliary valve; and

FIG. 11 is a modification of the apparatus showing its application to a multi-chambe-red device.

In FIGS. 1-4 for convenience of describing the cycle of this invention, the apparatus is shown in simplified form, the figure numbers corresponding to the steps of the cycle which will be described in detail below. In order to simplify the drawings and cycle presentation, the valves which are closed are indicated by an x in a circle, while those which are open are presented as an open circle and are labelled for ease of identification. Thus for example in FIG. 1 it will be seen that the lowpressure valve is open.

Turning now to FIG. 1, it is possible to identify the component parts of a typical refrigeration apparatus constructed in accordance with this invention. A fluid-tight enclosed space generally designated as 10 has movable Within it a displacer 1 1 which in its motion defines two chambers, an upper warm chamber 12 and a lower cold chamber 13. It will be appreciated that in eflect this is a single constant volume apparatus which has an upper or hot end and a lower or cold end, the hot and cold ends varying in volume during the refrigeration cycle. Thus the use of a single constant volume is a distinguishing feature which contrasts with the use of two chambers of varying volume as required in the no-Work cycle disclosed in U.S.P. 2,966,035. Suitable fluid-tight sealing means 14 are provided in conjunction with the displacer 11 and the displacer is mechanically joined to a suitable driving means through a shaft 15, which operates within a suitable sealing means 16.

It will be appreciated that the terms upper and lower are used in a relative sense, and that the refrigeration apparatus may be oriented in any manner, these terms being employed only to correspond to the orienta tion illustrated in the figures. In like manner, reference to the two chambers as hot and cold is made as a convenience in designating them, and the terms are only relative.

Associated with the refrigerator is a high-pressure fluid supply reservoir 18 and a low-pressure fluid exhaust reservoir 19 which in a closed system are connected through a conduit 34 having located therein a clean-up system 35 and a compressor 36. From high-pressure fluid supply reservoir 18 there is a high-pressure line 20 controlled by a valve 21, and from the low-pressure fluid exhaust reservoir there is a low-pressure fluid conduit 22 controlled by valve 23. Both of the conduits 20 and 22 discharge into a primary fluid path 25 which contains associated with it a primary heat storage means, typically a regenerator 26, and a suitable means 28 for delivering refrigeration to an external load. It will be appreciated that means 28 may be a heat exchanger or a heat station. In operation some form of control means which coordinates the movement of the displacer 11 with the operation of valves 21 and 23 must be provided. These may be any one of a number of suitable known control means which are generally illustrated in FIG. 1 to comprise a driving wheel 17, and two cams 21a and 23a which are mechanically connected (by means not shown) to valves 21 and 23, respectively. A suitable driving 3 means such as motor M is associated with this control means.

A separate and distinct secondary fluid path 30 communicates between the hot chamber 12 and the cold chamber 13, and has associated with it a secondary heat storage duit 22 into the low-pressure exhaust reservoiras a heat exchange liquid. Thus there is provided a heat station 32 which effects periodic out-of-contactheat exchange between hot fluid-t'ravelling from the hot chamber 12 into I the cold chamber 13 and the low-pressure fluid leaving the cold chamber 13 by way. of fluid path 25;

Before discussing the operational advantages present apparatus and cycle possess overfthepresent nowork apparatus and cycle, it will be helpful to describe l which the the refrigeration cycle which is performed in the appara- 'tus of this invention. This may be done with reference to FIGS. 14. It may be assumed that the cycle begins with the situation which obtains in FIG. 1A. The displacer is in its uppermost position having remained there throughout. the preceding step, and the valve tothe lowpressure exhaust reservoir is open. This means. that'the expansion of initially cooled high-pressure fluid which had been introduced into the cold chamber 13Vhas taken place throughout the cold. chamber and the two regenerators, and that the regenerators have been cooled. 'Dur ing this firststep then the expanded fluid is dischar'ged into the low-pressure exhaust reservoir, as well as into the hot chamber 12. That fluid entering the V low-pressure reservoir doesso by way of heat exchanger 28 and retor 31 by virtue of the previous passage of cool lowpressure exhaust fluid through heat station 32. In regenerator 31 fluid from hot chamber 12 is further cooled such that when it enters thelower chamber 13, it also constitutes a supply of initially cooled high-pressure fluid.

vAt the endof step 3, the displacer. 11 has reached its uppermost position, and there .is'now high-pressure initially cooled fluid throughout the system.

Step4 comprises. the, opemng I of the low-pressure exhaust valvea-t which time expansion of the high-pressure initially cooled fluid-takes-place throughoutthe entire system. Further final-cooling and expansion are achieved in. the chamber 13 as.well as in regenerators 26 and 31. In this process, of course, the regenerators are cooled to store refrigeration for succeeding fluid which will enter "the system and the cycle has reached the state which is illustrated in FIG. 1 prepared to begin over again.

It is now possible'to described step 1 more fully. -At

' the beginning of step 1, thelow-pressure fluid in chamber 13.. is at a lower temperature than that of the highpressure fluid that filled chamber 13 by virtue of the adiabatic expansion of the residual fluid in chamber 13 from high pressure 'to low-pressure; The downward movement of the displacer, 11 expels mostof the fluid in chamber 13 initially through heat exchanger 28. In

this heat exchanger 23 the temperature of thefluid can be raised to substantially the temperature of the fluid in generator 26,while that fluid entering the hotchamber A 12 does so byway of the secondary regenerator 31. In passingthrough the regenerators 26 and 31,'the cold expanded fiuid-furthercools the regenerators thus storing the refrigeration for a succeeding step in the cycle. .At

the end of step .1 the displacer has reached its lowermost position.

Throughout step 2 the displacer-is retained in this lowermost position and the" high-pressure valve to the high-presstirefluid supply reservoir is opened, while the low-pressure exhaust valve isflclosed. Under these circumstances, high-pressure fluid is supplied by way of regenerators. 26 and 31 into the hot chamber 12, and in its passage into chamber 12 thefluid is cooled to some.ex-.

.tent by reason of the refrigeration stored in the regenerators 26 and 31 during step 1.' The introduction of highpressure fluid into chamber '12serves to compress residual fluid" remaining in thelc'hamber'and thus to generate heat of compression. L The result of the. supplying .of high- .pressure fluid to the system is therefore the'heating of the fluid in chamber '12 to a temperature considerably chamber 13 before its expansion, thereby providing refrigerationto a heatsourceconnected to .heat exchanger 28. This low-pressure fluid then enters the cold end of the regenerator 26 *at substantially the .same temperature as that of the high-pressure fluid leavingregenerator 26 during the pressurizing of chamber 13 instep 3.. During passage of this fluid through the regenerator 26, heat is extracted from the regeneratormatrix to increase the temperature ofthe fluid so that on leaving the regenerator 26 at. the warm' end the fluid temperature is substantially the same as that temperature of the entering high-pressure fluid during. step 3 which is the temperature of the supply fluid from the high-pressure reservoir. 18. This fluid then passes throughheat station 32 where it picks up further heat and enters the low-pressure reservoir 19 at a temperature higher than thatof the supply fluid from reservoir 18. Since the temperature of the fluid leaving the system'is higherthan that entering, .thermal energy has been extracted-from the system,'the magnitude of which'is substantially the same as the net refrigeration produced. .The. downward movement of the displacer 11 also transfers some low-pressure fluid. from chamber 13 .through regenerator 31 to chamber 1210 form the residual fluid infthat chamber at the beginning of step .2.

above'that'at which the high-pressure fluid entered the refrigerator. Thus, at the end of step 2 there is present in chamber 12 a quantity offhigh-pressure hot fluid.

During step .3 the supplying of-high-pressurefluid into the refrigeration systemis continued... In its passage through regenerator 26, the high-pressure fluid is initially cooled;by-reason -of the refrigeration stored within this ,regenerator, and it therefore enters cold chamber 13 in an initially. cooled high-pressure state. With the movementofthedisplacer 11 in an upwardly direction as indicated in FIGS. 3Aand 3B,.the initiallycooled high- ,pressurefluid fillschamber 13 .and the hot fluid present This fluid, in passage through regenerator'31 to chamber 12, extracts heat from the regenerator 31t0 enter chamber 12 at substantially the same temperature as the fluid had on leaving chamber12- in step 3. In step 2 the residual fluid in chamber 12is compressed from low pressure to highpressure, by the supply of high-pressure fluid through regenerators26 -and 31 and so. develops heat of compression in the chamber '12. In step 3, whenthe fluid in chamber 12 is transferred tochamber 13, the fluid first passes through heat station 32 togive up its heat of compression'to that heat stationand later in steps 4 and 1 in chamber1-2 isalso transferred to chamber .13 being cooled first in heat station 32 and then'insecondary.

.regenerator 31. In the process of this latter fluid trans fer, heat is stored in'the heat station 32 and the fluid is cooled atleast partiallyby the time it reaches r'egenerato theexhaustlow-pressure fluid before entering lowpressure reservoir 19."

From a description of the cycle of this invention, it can be shown that it possesses certain distinct advantages over that which is associated with the no-work cycle of U.S.P. 2,966,035. These advantages may be discussed .end with the incoming high-pressure supply gas as there First, there is no mixing ofthe heated gas at the hot is in the no-work cycleof U.S.P. 2,966,035. All of the gas which is supplied into hot chamber 13-comes by way of thesecondary regenerator 31 and leaves by this regeneratorto with the additional supply of highbefore bottom dead center.

erator to fill the hot end under pressure.

pressure fluid in step 3. This in turn means that the temperature differential across the main regenerator 26 is less and therefore the regenerator 26 is potentially more efiicient. The pressure drop across the displacer 10 is less in this cycle and apparatus since it is due only to the gas flow involved in the emptying and filling of the hot end or hot chamber 12. This is to be distinguished from that in the no-work cycle of U.S.P. 2,966,035 in which the pressure drop across the displacer is due to the filling of the cold chamber (i.e., chamber 13) in that cycle.

Any solid contaminants, i.e., fluids with higher freezing points than the refrigeration fluid being used, are deposited in the main regenerator 26; and while an increased pressure drop across this regenerator 26 due to contamination plugging (freezing of the contaminant fluids) may reduce the gross refrigeration, the gas circulating through the secondary regenerator 31 is always clean since contaminants have been frozen out, so that the AP or pressure drop affecting the driving load required by the diplacer is much less and remains constant throughout the operation of the refrigerator. This in turn results in requiring less work input into this apparatus for it will be appreciated that it is always necessary to supply a small amount of work input to control the movement of the displacer since its natural tendency is to move in a direction opposite to that which is required by the cycle.

Another advantage which arises from the present methd and apparatus is due to the fact that the heated gases which rise to their temperature through initial compression are always swept to the hot end of the constant volume, namely, to the top end of chamber 12, while the cooled gases which are due to expansion are always swept to the cold end. Thus there is no opportunity for unwanted heat transfer. Because of the reduced pressure drop across the displacer, the burden on the seal 14 is somewhat lessened and therefore friction due to this seal can be reduced.

In a typical system such as the no-work cycle of U.S.P. 2,966,035, which has sinusoidal displacer motion, the high-pressure supply valve i typically opened about 20 In this case the displacer is moving down, and on opening the high-pressure valve thepressure drop through the regenerator gives an additional thrust downward overriding the displacer drive.

This force reversal which is repeated on exhaust just before top dead center creates a considerable burden on the drive mechanism and particularly the gears of the apparatus. However, in the apparatus of the present invention the initial shock thrust due to pressurization is in the opposite direction, that is, toward the hot end which causes no reversal shock on the drive mechanism. Thus the apparatus of this invention presents less problems in mechanical design particularly when it is adapted to large-scale refrigeration devices.

Finally, the heat generated in the hot chamber 12 can easily be removed by suitable heat station means with the exhausting low-pressure gas. It will be appreciated that this heat exchanger must be of the type which is capable of temporarily storing heat inasmuch as heat is given up to the heat storage means 32 by the hot highprcssure fluid being transferred from chamber 12 to chamber 13 at a time when no low-pressure gas is exhausting. However, when the low-pressure gas is exhausted in steps 1 and 4, the heat can be removed from the heat station by the passage of this fluid into the low-pressure fluid exhaust reservoir. It should be added that the higher the temperature at the hot end, or in the hot chamber 12, the less fluid flow is required through the regen- Thisin turn means that an equal amount of refrigeration can be obtained from a smaller amount of fluid flowing within the system.

, FIG. illustrates a modification of the apparatu of this invention which operates on the same cycle as described above. In this modification the energy delivered external of the system is part thermal and part mechanical by virtue of the presence of a piston portion in the sliding body which is used in place of the displacer 10 of FIG. 1. Thus in the apparatus in FIG. 5 there is provided an enclosed space 40 which has a stepped configuration having a lower portion 41 and an upper portion 42, the latter being of a somewhat smaller diameter than the former. Within this enclosed space is a sliding body which comprises a lower portion 44 which can be considered to be a displacer and an upper portion 45 which can be considered to be a piston. Actually, in analyzing the apparatus, the piston 45 can be thought to extend down through the displacer as illustrated by the dotted lines. An additional fluid-tight seal 46 is required because of the pressure differential which exists between the upper hot chamber 48 and the atmosphere. There is also a somewhat greater pressure differential between the upper hot chamber 48 and the lower cold chamber 49 than exists in the apparatus of FIG. 1.

The apparatus of the FIG. 5 modification actually combines the no-work cycle and apparatus with a work cycle and apparatus, the latter being one in which mechanical energy is delivered external of the system. Thus it can be shown that by the use of a displacer-piston type sliding body such as is illustrated in FIG. 5, it is possible to take advantage of the fact that the work cycle portion of the apparatus delivers mechanical energy while the no-work cycle portion requires mechanical energy. These can be used to offset each other so that the apparatus is in effect a self-sustaining one as far as energy balance is concerned. In a no-work cycle it is necessary to supply some mechanical work to the system to drive the displacer, such as by shaft 15. An analysis of the cycle will indicate that the direction of the displacer motion is in fact opposed to that which would be the natural motion of the displacer within the system. Thus difficulties arise in providing gears which are durable enough to perform the operation in the no-work cycle over extended periods of time, particularly in large-sized equipment. In contrast to the no-work cycle, the work cycle (see for example U.S.P. 2,906,101) is capable of delivering mechanical energy external of the system, but when the work cycle is performed in large-sized apparatus the amount of mechanical work which must be stored and dissipated requires excessively rugged mechanisms and an excessively large flywheel when the apparatus is driven at the slow reciprocating speeds which are preferred for this type of apparatus. However, the apparatus of FIG. 5 combines the work and no-work apparatus and results in an improved refrigerator which possesses the inherent advantages of both of these apparatus and at the ame time affords the possibility of balancing the work required in the no-work cycle to move the displacer against the work which is delivered in mechanical form external of the system in the work cycle. This is particularly true if the apparatus is to be used in largesized refrigeration devices where such mechanical diificulties are multiplied.

FIGS. 6-8 illustrate modifications in the regenerators of the apparatus of this invention. In FIG. 6 the secondary regenerator 53 is located within displacer 52, thus forming an internal fluid path between chambers 12 and 13. Typically, the regenerator 53 may be perforated copper disks or copper screens stacked within the space 53. The fluid conveniently enters and leaves the regenerator 53 by means of passages 54.

In FIG. 7 the secondary regenerator is also internal of the housing defining the enclosed space 10, but in this case it takes the form of an annular ring around the displacer. This annular regenerator 56 may typically be wire as shown, copper screening or perforated copper disks held in spaced relationship. FIG. 7 also shows the incorporation of a heat station 57 in the bottom portion of the enclosed space. This heat station is also annularly shaped such that it defines a cylindrical passage in which the displacer 11 moves. Heat transfer fluid conduit means 58 are wrapped in thermal contact around the refrigerator at the bottom end corresponding generally to the location of theheatstation'within therefrigerator. Refrigeration shown in FIG,- 6 "Thus, the regenerators required in' the apparatus of this invention may take many forms and any of those which would be used by those skilled in the art are contemplated as falling within the scope of thissdisclosure. I j '7 Y FIG. 9gshows another modification of the apparatus in which theresis provided an auxiliary conduit 60 which communicates between the fluid path and the upper hot chamber 12. Flow of fluid within this path is controlled by valve 61. The operation of this valve is illustrated in FIG. 10, and it will be seen that after initial pressurization-of t he system with valve 61 closed it may then be opened during the displacers upward motion during step 3. Some of the gas displaced from the hot chambe r 12 will mix with the incoming high-pressure gas entering chamber 12 through conduit 60 in both regenerators 26 and 31. --Thus, the heat generated in the system can be taken up by the exhaust, gas directly as in the no-work cycle of U.S.P. 2,966,035. In a similar manner, valve 61 may be closed during the initial depressurization of the cycle (step '4) and then opened; This means that valve .61 is closed only duringtheperiods of initial pressurization and depressuriz ation to' effect-a damping of the dis placer motion to counteract that which would normally occur,;and in this role ithas an important function as a dampening meansa a a Final1y, FIG. 11 illustrates the apparatus of this invention in the-form of a multi-chambered device in which of a stepped configuration made of sections 66, 677, and

68, and which in its vertical move'ment defines three cold chambers of successively colder temperatures, namely, 70, 71 and 72. The primary regenerators are associated with each of the cold chambers and are in a fluid path made up of conduits 79,; 80 and 81. In this apparatus it is necessary to supply'only one'secondary regenerator and fluid path, namely path 30, with its regenerator 31, whichcommunicates between the hot chamber the first of the cold chambers 70.

12 and It will be apparent from the above description and drawings that there is provided a'novel apparatusand method for generatingrefrigeration. Moreover, this is an improvement over the present no-work cycle in that the use of a single constant volume chamber which hasa hot and a cold end, and the use of a secondary regenerator and a fluid path between the hot and cold'ends permit .minimizing pressure and temperature'drops across the regenerators as well as the pressure drop-across the displacer, These improvements'result in better performance, as discussed in detail above. 1

It'will thus be seen that the objects set forth above, among those made apparent from the preceding descrip- 8 companying drawings shall be interpreted as illustrative and not inalimitingsensel V I claim: Y 1. A fluid expansion refrigeration method, comprising thesteps of V (a) supplying high-pressure fluid indirectly in heat ex- 1 change with a heat storage matrix to one end of an 1 enclosed space of constant volume thereby compressing residual fluid containcd -therein and generating heat to-raise the temperature of, said high-pressure V fluid supplied and providing a first quantity of hot n 'high-pressure'fluid; 1 K I a '(b)l transferring said first quantity of hot high-pressure fluid to the. other end of said enclosed space and during said transfer cooling said high-pressure fluid to provide a quantity of initially cooled highpre-ssure fluid; (o); supplying directly to said other end of said enclosed space a further quantity of initially cooled high-pressure fluid to form with the other quantity a total charge of initially cooled high-pressure fluid insaid other end; and Y (d) exhausting said'total charge of initially cooled V high-pressure fluid to a low-pressure region and to said one end at low pressure therebyvto expand it and further cool it whereby said other end of said enclosed space is capable of delivering refrigeration externally thereof. 2. Refrigeration method in accordance with claim 1 wherein said cooling of said hot high-pressure fluid in a step (b) is accomplishedin part by out-of-contact heat exchange with a heat exchange fluid.

V 3. Refrigeration methodv in accordancewith claim 2 wherein said heat exchange fluid is the expanded fluid exhausted ,to said low-pressure region in step (d).

4. Refrigeration method in accordance with claim 1 wherein said cooling of said hot high-pressure fluid in step *(b) is accomplished in part by contact with thermal there are provided a seriesof successively colder chamtion, are efficiently attained, and, since certain changes may be made in carrying out the'above method and in the constructions set forth without departing from the scope of the inventiomit is intended that all matter contained in the above description as are shown in the acstorage-surfaces cooled in exhausting said high-pressure fluid to said o ne end in step (d). I

5. Refrigeration method in accordance with claim 1 wherein said furtherquantity of vhigh-pressure 'fluid is initially cooled by cdntactiwiththermal storage surfaces cooled in exhausting said high-pressure fluid to said lowpressure region instep (d).

6. Refrigerationmethod in accordance with claim 1 wherein said other end of said enclosed space comprises ,a series of expandable chambers of successively lower temperatures. 1

7. A fluid expansion refrigeration method, comprising thestepsof Y (a) supplying a first quantity of highpres'sure.fluid :from a high-pressure fluid source by Way of primary and secondary fluid paths to the warm end of variable volume of an enclosed space of constant volume thereby to compress residual fluid in said Warm end and heat the high-pressure fluid in said warm end 1 while maintaining its volume constant; (-b) continuing to supply asecond quantity of said high- 'pressure fluid to the cold end of variable volume of said enclosed space along said primary fluid path .andlinitially cooling said high-pressure fluid while simultaneously transferring the heated first quantity of high-pressure fluid from said warm end along'said secondary fluid path to said cold end and initially cooling saidfirst quantity whereby the volume of said warm end is decreased to a minimumand the volume of said cold end is increased to a maximum; (c) expanding the high-pressure initially cooled fluid within said cold end and said primary and secondary fluid paths by exhausting said fluid to a low-pressure region while maintaining the volumes of said cold and warm ends essentially constant; and (d) discharging the'expanded finally cooled fluid to said low-pressure region by decreasing the volume of said cold end to a minimum and increasing the volume of said warm end to a maximum thereby to introduce said residual fluid into said warm end required in step (a) by way of said secondary fluid path.

8. A fluid expansion refrigeration method, comprising the steps of (a) supplying a first quantity of high-pressure fluid from a high-pressure fluid source by way of primary and secondary fluid paths to the Warm end of variable volume of an enclosed space of constant volume thereby to compress residual fluid in said warm end and heat the high-pressure fluid in said warm end while maintaining its volume constant;

(-b) continuing to supply a second quantity of said high-pressure fluid to the cold end of variable volume of said enclosed space along said primary fluid path and initially cooling said high-pressure fluid while simultaneously supplying an additional first quantity of high-pressure fluid to said warm end and transferring the heated first quantity of high-pressure fluid and said additional first quantity of high-pressure fluid from said warm end along said secondary fluid path to said cold end and initially cooling said first quantity whereby the volume of said Warm end is decreased to a minimum and the volume of said cold end is increased to a maximum;

(c) expanding the highressure initially cooled fluid within said cold end and said primary and secondary fluid paths by exhausing said fluid to a low-pressure region While maintaining the volumes of said cold and warm ends essentially constant; and

(d) discharging the expanded finally cooled fluid to said low-pressure region by decreasing the volume of said cold end to a minimum and increasing the volume of said warm end to a maximum thereby to introduce said residual fluid into said warm end required in step (a) by way of said primary and secondary fluid paths.

9. Fluid expansion refrigeration apparatus, comprising in combination (a) a fluid-tight enclosure;

(b) displacer means movable within said enclosure and defining therein a first and second chamber the volumes of which are controlled by the movement of said displacer means;

(c) a primary fluid path, incorporating thermal storage means, communicating with said second chamber;

(d) a secondary fluid path, incorporating thermal storage means, between said first and second chamher and in communication with said primary fluid path;

(e) a high-pressure fluid supply reservoir in communication with said primary fluid path;

(f) a low-pressure fluid exhaust reservoir in communication with said primary fluid path;

(g) valve means associated with said high-pressure and low-pressure reservoirs and adapted to admit high-pressure fluid to and release low-pressure fluid from said chambers; and

(h) control means coordinating said displacer means and said valve means, whereby high-pressure fluid is supplied to said first chamber by way of said primary and secondary fluid paths during the step in the refrigeration cycle in which said first chamber is at maximum volume and to said second chamher by way of said primary fluid path when said first chamber is decreasing in volume and fluid is exhausted from said second chamber during those steps in the refrigeration cycle in which said second chamber is at maximum volume and is decreasing in volume.

I :10. Apparatus in accordance with claim 9 wherein said displacer means incorporates a piston portion whereby said piston portion delivers work external of said enclosure to furnish at least a part of the energy required to drive said control means.

11. Apparatus in accordance with claim 9 further characterized by having heat exchange means associated with said secondary fluid path, said heat exchange means being adapted to effect out-of-contact heat exchange between fluid flowing in said secondary fluid path and a heat exchange fluid.

12. Apparatus in accordance with claim 9 wherein said secondary fluid path, incorporating thermal storage means, is internal of said displacer means.

13. Apparatus in accordance with claim 9 wherein said secondary fluid path, incorporating thermal storage means, is within said enclosure in the form of an annular cylinder defining the volume in which said displacer means moves.

14. Apparatus in accordance with claim 9 wherein said primary fluid path, incorporating thermal storage means, is within said enclosure in the form of an annular cylinder defining the volume in which said displacer means moves and said secondary fluid path, incorporating thermal storage means, is internal of said displacer means.

15. Apparatus in accordance with claim 9 further characterized by having valve-controlled fluid conduit means communicating between said primary fluid path and said first chamber.

16. Fluid expansion refrigeration apparatus, comprising in combination (a) a fluid-tight enclosure;

(b) displacer means movable within said enclosure and defining therein a first chamber and a series of second chambers of successively colder temperatures, all of said chambers having volumes which are controlled by the movement of said displacer means;

(c) a primary fluid path, incorporating thermal storage means, communicating with said series of second chambers;

(d) a secondary fluid path, incorporating thermal storage means, between said first chamber and the first of said series of second chambers and in communication with said primary fluid path;

(e) a high-pressure fluid supply reservoir in communication with said primary fluid path;

(f) a low-pressure fluid exhaust reservoir in communication with said primary fluid path;

(g) valve means associated with said high-pressure and low-pressure reservoirs and adapted to admit highpressure fluid to and release low-pressure fluid from said chambers; and

(h) control means coordinating said displacer means and said valve means, whereby high-pressure fluid is supplied to said first chamber by way of said primary and secondary fluid paths during the step in the refrigeration cycle in which said first chamber is at maximum volume and to said series of second chambers by way of said primary fluid path when said first chamber is decreasing in volume and fluid is exhausted from said series of second chambers during those steps in the refrigeration cycle in which said series of second chambers is at maximum volume and is decreasing in volume.

References Cited by the Examiner UNITED STATES PATENTS 2,567,454 9/5 1 Taconis 626 2,907,175 10/59 Kohler 62-6 2,966,034 12/ 60 Giflord 62-6 2,966,035 12/60 Gifford 626 3,119,237 1/ 64 Gifford 626 RDBERT A. OLEARY, Primary Examiner.

WILLIAM J. WYE, Examiner. 

1. A FLUID EXPANSION REFRIGERATION METHOD, COMPRISING THE STEPS OF (A) SUPPLYING HIGH-PRESSURE FLUID INDIRECTLY IN HEAT EXCHANGE WITH A HEAT STORAGE MATRIC TO ONE END OF AN ENCLOSED SPACE OF CONSTANT VOLUME THEREBY COMPRESSING RESIDUAL FLUID CONTAINED THEREIN AND GENERATING HEAT TO RAISE THE TEMPERATURE OF SAID HIGH-PRESSURE FLUID SUPPLIED AND PROVIDING A FIRST QUANTITY OF HOT HIGH-PRESSURE FLUID; (B) TRANSFERRING SAID FIRST QUANTITY OF HOT HIGH-PRESSURE FLUID TO THE OTHER END OF SAID ENCLOSED SPACE AND DURING SAID TRANSFER COOLING SAID HIGH-PRESSURE FLUID TO PROVIDE A QUANTITY OF INITIALLY COOLED HIGHPRESSURE FLUID; (C) SUPPLYING DIRECTLY TO SAID OTHER END OF SAID ENCLOSED SPACE A FURTHER QUANTITY OF INITIALLY COOLED HIGH-PRESSURE FLUID TO FORM WITH THE OTHER QUANTITY A TOTAL CHARGE OF INITIALLY COOLED HIGH-PRESSURE FLUID IN SAID OTHER END; AND (D) EXHAUSTING SAID TOTAL CHARGE OF INITIALLY COOLED HIGH-PRESSUE FLUID TO A LOW-PRESSURE REGION AND TO SAID ONE END AT LOW PRESSURE THEREBY TO EXPAND IT AND FURTHER COOL IT WHEREBY SAID OTHER END OF SAID ENCLOSED SPACE IS CAPABLE OF DELIVERING REFRIGERATION EXTERNALLY THEREOF. 